Lithium-based batteries are a well-established technology. In a typical lithium-ion battery during discharge, lithium ions transfer from the metallic lithium component of the anode electrode into an electrolyte leaving an electron behind. These lithium ions (Li+) then circulate as positive ions in the electrolyte and replace the lithium ions consumed at the lithium-ion battery cathode. In the lithium-air battery, oxygen is generally introduced into the electrolyte at the cathode by being passed through pores in such cathode. Oxygen molecules are reduced at the cathode by acquiring electrons to become negative oxygen ions. The oxygen ions then combine with adjacent lithium ions to produce lithium peroxide and/or lithium oxide. The electrical charges associated with these reactions pass externally between the electrodes providing an external current.
The process in the lithium-air battery can be reversed by forcing charge in the opposite direction causing the dissociation of the lithium oxides to reform lithium ions which replace the lithium ions that become deposited as metallic lithium on the anode. Simultaneously, gaseous oxygen (O2) is evolved.
In many of the electrolytes used in the above described arrangement the lithium oxide or peroxide, once formed, is relatively insoluble and tends to plug-up the permeability of the electrode supplying oxygen to the reaction, obstructing some electrode regions and blocking further reduction of oxygen. As a consequence, the reaction does not persist in performing at an optimal level.
It is known to use a molten electrolyte in association with lithium to produce a single use primary battery or thermal battery that can be stored indefinitely so long as the electrolyte is in a solid phase. To activate the thermal battery, the electrolyte is quickly heated and becomes an excellent ionic conductor in the form of an ionic liquid.
An example is U.S. Pat. No. 8,039,138 issued Oct. 18, 2011 to the present inventor Melvin Miles and others which focuses on the feature that such a battery is preferably chloride-free, sodium ion-free, and water-free when using molten nitrate electrolytes. A related reference is U.S. Pat. No. 7,629,075 to the present inventor. Advantages of these references include significantly higher cell voltages and improvements in energy and power density. Additionally, harmful gas-evolution reactions are addressed by eliminating chloride ions, sodium ions, and moisture contaminants.
This present invention addresses a new arrangement for a rechargeable lithium-based battery that is based on use of a molten nitrate electrolyte containing sufficient lithium ions combined with providing oxygen to support the generation of electrical current.
The invention in its general form will first be described, and then its implementation in terms of specific embodiments will be detailed with reference to the drawings following hereafter. These embodiments are intended to demonstrate the principle of the invention, and the manner of its implementation. The invention in its broadest and more specific forms will then be further described, and defined, in each of the individual claims which conclude this Specification.